Re: [mpls] ahRE: draft-bashandy-mpls-ldp-bgp-frr-00 motivation

["Ilya Varlashkin" <[e-mail]>]

> -----Original Message-----
> The best current available mechanism is BGP PIC Edge that relay on IGP
> convergence to detect that remote PE is no longer reachable : PIC Edge
result
> mainly depends on how fast your IGP is converging (sub sec or more).
>

I've been recently measuring convergence on not very fast RP and found that
even for 10 000 nodes it's less than 900ms. Clearly 10K nodes is unlikely to
be seen in many networks if in any at all. And for real-world sized nets
convergence is like few tens of ms - not really to worry about.
 
> Ahmed solution is an FRR solution so doesn't rely on convergence. As soon
as
> a P router detects that the link to the protected PE fails, it will switch
(using
> pre-programmed backup NHLFE), so there you are in FRR numbers ... 50msec
> - 100msec depending of implementation ...
> 

If _P_ node needs to do fail-over to backup PE depending on VPN (L3VPN, PWE,
L2VPN etc) then _P_ node needs to have VPN-level knowledge, and that
contradicts with original idea of P nodes (they shouldn't care what's
inside, only how to get to the edge independent of "payload").

> Clearly the solution is today complex, and I hope it could be a bit
simplified :)
>

Because of previous statement I see proposed solution as complication rather
than simplification, and because of above mentioned IGP convergence times
the gain seems to be too little when balanced against complexity.
 
/iLya